Fraudulent transactions, whether executed online by a malicious party who has stolen a user's online banking password or offline by a malicious party entering a restricted building using a forged identification card, are indicators of a lack of authentication in present day security systems. Similarly, authorization (permission to complete a transaction) is limited without a strong notion of authentication. Traditionally, techniques for authentication are classified into several broad classes such as “what you know” (e.g., passwords or a social security number), “what you have” (e.g., physical possessions such as ATM cards or a security dongle), and “what you are” (e.g., biometric information such as a finger print or DNA). However, many of these solutions are burdensome to users, requiring the user to remember information or carry extra devices to complete a transaction. Thus, there is a need in the digital security services field to create a new and useful system and method of notifying mobile devices to complete transactions. This invention provides such a new and useful system and method.